We used mist netting in the Chamela-Cuixmala Biosphere Reserve to assess the population phenology of the Flammulated Flycatcher (Deltarhynchus flammulatus), a poorly-known dry forest endemic of the Mexican Pacific Slope. We captured 135 birds (first records only) during 23,515 net hrs over a period of several years which suggests this flycatcher is common at the reserve. Monthly averages of captures (including monthly recaptures) differed between seasons with a peak (71%) during May to August (end of dry season to middle of wet season) and fewer (29%) captures during the rest of the year. Flammulated Flycatchers in breeding condition (n  =  38) were captured in June and July. Hatching year birds (n  =  8) were captured from 10 July through 11 December. We found an active nest in a cavity on 29 June 2010. We observed pieces of snake skin lining the nest, which may indicate a closer relationship with Myiarchus. Additional knowledge on the ecology and breeding biology of the Flammulated Flycatcher is urgently needed for development of effective conservation plans.